Increasing the amperage-output on 1960's--'80's Chrysler-vehicle generating systems

To improve upon the electrical generating output of the stock Chrysler alternator of the 60-to 70-amp type, the newer Chrysler 100-amp alternator can be employed.

If you go to an automobile salvage yard, you should be able to find the necessary bracket for the relevant engine, i.e. the smaller 318-340 and 360 cu. in. engine, or the larger-blocked engines--361, 383, 413, 426 hemi and 440 cubic inch.

With the 100-amp alternator bracket, the 100-amp alternator can be installed on Chrysler vehicles that have the earlier, smaller alternators with the dual-drive-belt pulley. I've done it; it wasn't very difficult. My car was a '72 mid-size Plymouth with a 318 engine. The same electronic voltage regulator is to be used with the larger, 100-amp alternator. Chrysler Motors was very good for standardizing part use.

Without increasing the output wire's size of the car's wiring harness, the result was excellent! While the engine speed was at less than idle (automatic transmission engaged), and a heavy electrical load of headlights, breaklights and AC blower set to high, the ammeter didn't at all dip into the discharge side of the scale as happens with the smaller alternators. This test, as you might imagine, simulates a stop at a traffic light on a hot summer night.

The electronic voltage regulator, which was introduced on Chrysler vehicles in 1969 to replace the earlier electro-mechanical regulators, is much better. If you want to use the electronic version on a pre-'69 model, you can without much difficulty. The electronic regulators require an isolated-field alternator. You'll have to replace your alternator, if it hasn't been already, with the isolated-field type which was stock on the '69 and up models.

Many rebuilt alternators sold for vehicle maintenance are of the isolated-field type. They come convertible with a jumper wire to connect one of the field-winding brushes to ground for replacement in a pre-'69 car with the earlier voltage-regulator alternators. The earlier type's rotor winding was grounded at one side via one of the two brushes. The newer electronic regulator wiring requires an isolated rotor (ungrounded).

So if your pre-'69 car's alternator has been replaced with one of these convertible types, you just disconnect one brush from ground and proceed with the rewiring to accommodate the new electronic regulator.

By the way, your motor vehicle's alternator is a 3-phase alternating current (AC) generator as is your electric power company's, but with the difference of having means for converting the AC to direct current (DC). This rectification (as it's referred to), is accomplished by the use of a diode bridge. Six diodes are employed, two for each phase, yielding full-wave rectification for each of the three phases.

There is one other difference; the power company's generators are governed to spin at a constant speed to maintain the 60-cycle-per-second (or 60 Hz) frequency which we use in North America. Your car's generator is conveniently driven by the engine which, of course, spins at varying speeds. As the final (rectified) output of your car's generator is DC, there is no concern of AC frequency (above a good operating-speed minimum), so the fluctuation of generator speed is moot.

Richard Stuart Otto, 14 Oct. 2007